import java.io.IOException;
import java.util.Iterator;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

/**
 * Created by ospip on 2019/3/19.
 * Copyright (c) 2019 LLAP. All rights reserved.
 */

public class WordCount {
    public WordCount() {
    }

    /*
    mvn package
    then run the JAR FILE (not class file!)
     */
    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();

        System.setProperty("HADOOP_USER_NAME", "hadoop");
        conf.set("fs.defaultFS", "hdfs://localhost:9000");
        conf.set("fs.hdfs.impl", "org.apache.hadoop.hdfs.DistributedFileSystem");

        conf.set("mapreduce.app-submission.cross-platform", "true");
        conf.set("yarn.resourcemanager.hostname", "localhost");
        conf.set("mapreduce.framework.name", "yarn");
//        conf.set("yarn.resourcemanager.address", "localhost:8088");


        /*String[] otherArgs = (new GenericOptionsParser(conf, args)).getRemainingArgs();

        if(otherArgs.length < 2) {
            System.err.println("Usage: wordcount <in> [<in>...] <out>");
            System.exit(2);
        }*/

        String[] otherArgs = new String[]{"hdfs://localhost:9000/user/hadoop/input", "hdfs://localhost:9000/user/hadoop/output"};

        Job job = Job.getInstance(conf, "word count");
//        conf.set("mapreduce.job.jar", "G:\\Java\\大数据及其应用（2019）\\target\\big-data-and-application-2019-1.0-SNAPSHOT.jar");
        job.setJarByClass(WordCount.class);
//        job.setJar("hadoop_job.jar");
        job.setUser("hadoop");
//        job.setJar("WordCount.jar");
        job.setMapperClass(WordCount.TokenizerMapper.class);
        job.setCombinerClass(WordCount.IntSumReducer.class);
        job.setReducerClass(WordCount.IntSumReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);

        for(int i = 0; i < otherArgs.length - 1; ++i) {
            FileInputFormat.addInputPath(job, new Path(otherArgs[i]));
        }

        FileOutputFormat.setOutputPath(job, new Path(otherArgs[otherArgs.length - 1]));
        System.exit(job.waitForCompletion(true)?0:1);
    }

    public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
        private IntWritable result = new IntWritable();

        public IntSumReducer() {
        }

        public void reduce(Text key, Iterable<IntWritable> values, Reducer<Text, IntWritable, Text, IntWritable>.Context context) throws IOException, InterruptedException {
            int sum = 0;

            IntWritable val;
            for(Iterator i$ = values.iterator(); i$.hasNext(); sum += val.get()) {
                val = (IntWritable)i$.next();
            }

            this.result.set(sum);
            context.write(key, this.result);
        }
    }

    public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable> {
        private static final IntWritable one = new IntWritable(1);
        private Text word = new Text();

        public TokenizerMapper() {
        }

        public void map(Object key, Text value, Mapper<Object, Text, Text, IntWritable>.Context context) throws IOException, InterruptedException {
            StringTokenizer itr = new StringTokenizer(value.toString());

            while(itr.hasMoreTokens()) {
                this.word.set(itr.nextToken());
                context.write(this.word, one);
            }

        }
    }
}